Burner control system



Oct. 28, 1941.

DU WAYNE J. PETERSON BURNER CONTROL SYSTEM Filed Feb. 25, 1938 g R 5. oo

km mm N? MT Zhwentor DmWmgnre J Pefiterson attorney Patented Oct. 28, 1941 S PATENT OFFICE BURNER CONTROL SYSTEM Application February 25, 1938, Serial No. 192,515

UNITED STATE 12 Claims.

My invention relates to a burner control system, and more particularly to one employing a pressure motor operated fuel valve.

In the copending application of Frederick D.

Joesting, Serial No. 87,716, filed June 27, 1936, now Patent 2,118,886 issued May 31, 193a, there is disclosed a burner control system wherein a pressure motor operated valve is used for controlling the flow of fuel to a main burner and wherein the pressure motor is controlled by a control member which is positioned by an electromagnetic structure comprising an armature and an electromagnet which is of sufficient strength to hold the armature and electromagnet together but of insufficient strength to move the members together. In the device according to this Joesting application, the electromagnet is energized according to the condition of the pilot flame so as to hold the control member for the pressure motor in a position wherein the fuel valve is open so long as the pilot burner is isnited. Manual means is provided in the above described arrangement for effecting the engagement of the armature and electromagnet when these members v are separated by deenergization of the electromagnet. The arrangement according to the Joesting application has the disadvantage that it is not adaptable for incorporation in a completely automatic system. The arrangement necessitates manual lighting of the burner and manual manipulation of the resetting means referred to. Since such fuel systems are quite hazardous, particularly where the fuel is gas, it is the customary procedure for the companies in chargeof the equipment to send out service men for relighting the pilot burner when it is extinguished. This practice is, of course, extremely costly.

An object of the present invention is to provide a pressure motor operated valve in which a control member therefor is held in one position by an arrangement comprising an armature and electromagnet capable of holding but not of moving the electromagnet and armaturel together and in which a supplementary motor means is provided for moving the electromagnet and armature together.

A further object of the invention is to provide an arrangement such as set forth in the previous object in which a thermo-couple is employed for energizing the electromagnet.

A further object of the invention is to provide a burner control system employing a valve according 'to the previous objects for controlling the flow of fuel to a main burner in which the energizaticn of the electromagnet is controlled by means responsive to a condition of the flame of a pilot burner.

A further object of the invention is to provide a burner control system in which a valve con= trolling the flow of fuel to the burner is held in open position by an electromagnetic arrangement comprising an armature and electromag net energized in accordance with the condition of the burner flame, in which a power operated motor means is provided for initially moving said armature and electromagnet into engagement, and in which upon energization of said electromagnet, said motor means is deenergized.

A further object of the present invention is to provide a burner control system of the type set forth in the preceding object in which ignition means is provided and in which the motor means and ignition means are energized and deenergized at approximately the same time.

A further object of the invention is to provide an improved burner control system with a normally constantly burning pilot burner in which upon a call for heat and upon the pilot burner being extinguished, the pilot burner is automatically reignited. 7

Other objects of the invention will be apparent from a consideration of the accompanying specification, claims and drawing.

In the single figure of the drawing, the burner control system of the present invention is shown in schematic form. For a more detailed understanding of the present invention, reference is made to this drawing.

In the drawing, a gas burner is designated by the reference numeral 10. This gas burner may be of any suitable conventional form. The burner is supplied with gas through a pipe H. Associated with the main burner I0 is a pilot burner I! supplied with gas through a pipe l3. Also located adjacent to the burner i0 is a bleed gas burner IE which is supplied with gas by a pipe iii. The main burner ill, the pilot burner l2, and the bleed gas burner l4 together with the right-hand portions of the pipes communicating therewith are shown considerably reduced with respect to the rest'of the apparatus, in order to more clearly illustrate the novel portion of the invention.

Loeated adjacent to the pilot burner i2 is a pair of spaced ignition electrodes H and is. These electrodes are energized by a stepup transformer 19 having a low voltage primary 20 and a high voltage secondary M. The high voltage secondary an is connected by conductors 22 and 23 to the electrodes l1 and I8, respectively. It will be obvious that energization of the primary 28 results in a potential being established between electrodes l1 and I8 to cause a spark therebetween.

The pipe H is threadedly connected with a valve housing generally designated by the reference numeral 25. This valve housing comprises a lower casing member 26 and an upper casing member 21 between which is clamped a diaphragm 28. The lower casing member 26 is provided with a recessed portion 29 forming an outlet chamber with which communicates the pipe The upper edge of the recessed portion 29 is provided with a flange 38 which forms a valve seat for a valve .member 32. Valve member 32 is secured to an arm 33 which is pivotally mounted at 34 on a bracket 35 secured to the lower casing member 26. The left-hand end of the arm 33 is slotted as indicated at 36. Cooperating with this slotted portion is a generally cylindrical member 31 which has an aperture 38 extending longitudinally therethrough. Member 31 is provided with a pair of flanges 39 and 48. The slotted portion 36 of arm 33 extends between the two flanges 39 and 48. A nut 42 serves to clamp member 31 to the diaphragm 28, washers 43 and 44 being placed adjacent to the diaphragm. It will be noted that the assembly formed by the tubular member 31 and arm 33 forms a connection between the diaphragm 28 and the valve 32 whereby any movement of the diaphragm 28 is transmitted to the valve 32. A gas supply pipe 46 is connected with the lower casing member 26. The pipe 46 leads from any suitable source of gas (not shown).

A passage 41 extends through the lower wall of the lower casing member 26, this passage communicating with a pilot valve chamber 48. Chamber 48, in turn, connects with a passage 49, which passage communicates with pipe |3 leading to the pilot burner |2. Controlling the connection between passage 41 and chamber 48 is a pilot valve Pilot valve 5| is provided with a stem 52, which extends through the upper wall of another casing member 53. This casing member 53 is secured to the valve housing 25 by any suitable means not shown, and a portion of the upper wall of the same forms the lower wall of the valve chamber 48. Valve stem 52 is provided with a collar 55 adjacent its lower end and between this collar 55 and the lower surface of the upper wall of casing 53, a spring 56 is interposed. Spring 56 serves to bias valve 5| to open position.

As will be pointed out in more detail later, a certain amount of the gas entering the lower casing member 26 passes through the passage 38 into the upper casing member 21. Communicating with the interior of the casing member 21 is a passage 58 which, in turn, communicates with a passage 59. Passage 59 is, in turn, adapted under certain "circumstances to communicate with a control valve chamber '68. The control valve chamber 60, in turn, is connected with a pipe 6|, which is connected through 'a valve 62 with a pipe l5 leading to the bleed gas burner l4. Communication between passage 59 and valve chamber 68 is controlled by a valve 84 which is provided with a valve stem 65 extending through the upper wall of casing member 53. As in the case of the pilotvalve 5|, the valve stem 65 of valve 84 is provided with acollar 66 adjacent its lower end and interposed between this collar and the lower surface of the.

upper wall of casing member 53 is a spring 81 which serves to bias valve 64 towards open position.

With all of I the burners completely extinguished, the valves 5| and 64 are biased to closed position in spite of springs 56 and 61. It will be noted that a lever member 69 abuts the lower end of both valve stems 65 and 52. This lever member 69 is pivoted at 18 to a stem member 1|, which stem member is provided at its upper end with a flange 12. The stem member 1| extends through the upper wall of easing member 53 and interposed between flange 12 and this upper wall is a spring 13. The spring 13 is sufficiently stronger than springs 61 and 56 that when spring 13 is free to act, the valves 64 and 5| are moved to their seats in spite of springs 61 and 56. Under certain circumstances, however, the action of spring 13 is constrained. It will be noted that stem member 1| is secured at its lower end to an armature member 15, which is of suitable material of high magnetic susceptibility. Armature member 15 is adapted to cooperate with an electromagnet 16, which comprises a U-shaped core 11 and a winding 18. The core 11 is, like armature 15, of material of very high magnetic susceptibility. The winding 18 is also of extremely low resistance being made of relatively heavy wire. The winding 18 is connected through conductors 19 and 88 with a thermo-couple 82. The thermo-couple 82 is of conventional construction comprising two elements 83 and 84 of suitably dissimilar thermoelectriccharacteristics. Like the winding 18, the conductors 19 and 88 are of relatively large cross section and of high conductivity so as to ofler as little impedance as possible to the current generated by the thermo-couple 82. By reason of this fact, the electromagnet is able to hold the armature 15 in engagement with core 11 when the winding 18 is energized by reason of the thermo-couple 82 being heated by pilot burner |2. In spite of the high magnetic susceptibility of the armature and core members 15 and 11 and the low conductivity of the various electric conductors used in connection with the electromagnet 16, the electromagnet is not able to move the armature 15 into engagement therewith when once released. It is, accordingly, necessary to provide some means of so moving the armature 15. In'the arrangement of the previously referred to Joesting application, this means was a manual one. According to the present invention, an automatically operated means is provided for performing this function.

The lower wall of casing member 53, which is designated by the reference numeral 81, is removably secured to the casing member for convenient access to the interior there 1. This lower wall or cover has secured there the electromagnet 16. The cover 81 also has slidably mounted therein an armature member 88. This armature member is provided with extensions 89 and 9|. The lowermost extension 9| serves to slidably mount the armature 88 in the cover member 81 and the upper extension 89 is adapted to engage the left-hand end of lever 69. Cooperating with the armature 88 is a solenoid winding 98. Upon energization of the solenoid winding 98, the armature 88 is adapted to be moved upwardly to move the left-hand end of lever 69 upwardly in a manner to be described in more detail later.

The solenoid valve 62 comprises a valve mem- Y ber to which is secured a solenoid core 93 around accaoee armature 93 is adapted to engage a switch blade 95 which, in turn, is adapted to cooperate with a fixed contact 96. Upon energization of the winding 94, the core 93 is moved upwardly to open the valve and to move switch blade 95 into engagement with contact 96.

Controlling the energization of valve 62 and of the solenoid winding 90 and the ignition transformer I9 at certain times is a thermostat generally designated by the reference numeral 99. This thermostat may be located in the room being heated or at some other suitable control point. The thermostat is shown as comprising a bimetallic element I to which is secured a contact blade IOI adapted to sequentially engage with contacts I02 and I03. Upon a fall in temperature, blade, IN is first moved into engagement with contact I02 and subsequently into engagement with contact I03.

Also controlling the energization of the solenoid winding 90 and of the ignition transformer I9 is a switch comprising a switch blade I04 and a iixed contact I05. The switch blade I04 is yieldable in character and has its lefthand end secured to a block I01 of suitable insulating material which block is, in turn, secured to the cover member 81 of casing 53. Secured to switch blade I04 is an armature member I08. Armature I08 is, when the electromagnet I6 is deenergized, very slightly spaced from the core TI. By reason of the yieldability of switch blade I04 and by reason of the small spacing between the armature I08 and core "I'I, a very slight force is necessary to move the armature I08 into engagement with the core 'I'i. As will be pointed out later, the electromagnet I6 is capable of exerting suflicient force when energized to efiect such movement.

Secured to the lower cover member 81 is a switch casing II 0. Located within this switch casing is a pair of fixed contacts III and H2. switch blade member I I3 is adapted to move into escape.

engagement with contacts I II and H2 to electrically connect the same. This switch blade member I I3 is connected to apush button I I4 outside of the casing H0 and is biased out of engagement with contacts III and H2 by a spring I I 6. The contacts III and H2 are connected to the conductors I9 and 80 which, as previously explained, serve to connect the thermo-couple with the electromagnet. When the switch blade member II3 is moved inwardly to bridge contacts III.

and I I2, thermo-couple 82 is short-circuited.

A step-down transformer I20 is used to supply low voltage power for the operation of the system. This transformer comprises a line voltage primary I2I connected to any suitable source of power (not shown) and a low voltage secondary I22.

Uperation The varlouselements of the system are shown in the position which they occupy when the system is completely shut down by the opening of a switch I24. Let it be assumed that this switch I24 is closed and the temperature to which thermostat 99 is subjected falls to thepoint at which switch blade IOI is in engagement with both contacts I02 and I03." Under these circumstances, the following circuit is established to the winding 94 of the solenoid valve 62: from the right-hand ergization of the solenoid winding 94 and in the opening of the valve 62. The opening of the valve 02 is accompanied by the movement of switch blade 95 into engagement with contact 96. When this occurs, a holding circuit is established to the winding 94 as follows: from the right-hand end of secondary I22 through conductor I25, switch I24, conductor I26, contact I02, contact blade IOI, bimetal I00, conductor I 33, contact 96, switch blade 95, conductors I34, I29 and I30, winding 94, and conductors I3I and I32 to the other terminal of secondary I22. It will be noted that this new holding circuit is independent of the engagement of contact blade "II with contact I03 so that the solenoid winding 94 will remain energized until switch blade IOI separates from contact I02. In this manner, a differential is interposed between the opening and closing of solenoid valve 62 to prevent a chattering action as the thermostat moves towards or recedes from its contact.

The valve 62 is, in effect, connected in series with valve I54 to control the flow-of the gas from the interio of the upper casing 21 to the bleed gas burner I4. Until not only valve 62 but also valve 64 is opened, the gas passing through the passage 38 into the upper chamber 21 cannot The result is that the pressure on the two sides of diaphragm 28 becomes the same so that valve 32 is held on its seat by the weight of the various parts and also by the gas pressure on the valve itself. In order to open the valve 32, it is accordingly necessary to not only open valve 62 in the manner previously described but also to open valve 64. Since it is undesirable to have the main valve 32 open before the pilot burner is ignited, the apparatus is designed to prevent opening of valve 64 in any manner whatsoever prior to the ignition of the pilot burner.

By the improved arrangement of the present device, the pilot burner is automatically ignited upon a call for heat by the thermostat 99, when extinguished. When the thermostat blade IOI engages both contacts I02 and I03, as previously described, a circuit is not only established to winding 94 but also to solenoid winding as follows: from the right-hand end of secondary I22 through conductor I25, switch I24, conductor I26, contact I02, contact blade IOI, contact I03,

. conductors I21, I28, I29, and I40, solenoid winding 90, conductors MI and I42, switch blade I04, contact I05, and conductors I43 and I32 to the other terminal of secondary I22. As soon as switch blade engages contact 96, a holding circuit is established to solenoid 90 as follows: from secondary I22 through conductor I 25, switch I24, conductor I26, contact I02, contact biade iIlI, bimetal I00, conductor I33, contact 95, switch blade 95, conductors I34, I29, and I40, solenoid winding 90, conductors MI and I42, switch blade I04, contact I05, and conductors I43 and I32 to the other terminal of secondary I22. As in the case of the holding circuit for winding 94, this holding circuit is independent of the engagement of switch blade IOI with contact I03. The energization of solenoid winding 90 causes the armature 88 to move upwardly and, as previ- 'ergization of the winding 90.

movement of the right-hand portion of lever 03 also permits the spring 56 to move valve 5| to open position. The various elements are so designed that the movement of armature 88 is sufficient to carry armature member I5 into engagement with core 11 of the electromagnet I5. Thus as a result of the energization of winding 90, armature I5 is moved into engagement with the electromagnet I6 and valve 5i is allowed to be moved to open position by its biasing spring 56.

The movement of valve 5| to open position permits gas to flow to the pilot burner as follows: through pipe 46 into the lower casing member 26, through passage 41, valve chamber 48, passage 49, and pipe I3 to pilot burner I2. Simultaneously with the energization of the solenoid windings 94 and 90, the ignition transformer I9 is also energized as follows: from the righthand terminal of secondary I22 through conductor I25, switch I24, conductor I26, contact I02, contact arm IOI, contact I03, conductors I21 and I45, primary winding 20, conductors I46 and I42, switch blade I04, contact I05, and conductors I43 and I32 to the other terminal of secondary I22. As soon as the switch blade 95 engages contact 36, a holding circuit is established to primary 20 as follows: from the right-hand terminal of secondary I22 through conductor I25, switch I24, conductor I26, contact I02, contact blade IOI, bimetal element I 00, conductor I33, contact 36, switch blade 95, conductors I34, I20, and I45, primary winding 20, conductors I46 and I42, switch blade I04, contact I05 and conductors I43 and I32 to the other terminal of secondary I22. As in the case of the holding circuits for the other devices, it will be noted that the holding circuit for primary winding 20 is independent of contact I03. The result of the establishment of first the energizing circuit and then the holding circuit to primary winding 20 is that the ignition transformer I9 is energized and a spark is produced between electrodes I1 and I8. The gas being admitted to the pilot burner is now ignited by the spark with the result that the hot junction of thermocouple 82 begins to be heated. After this heating of the thermo-couple has been carried sufiiciently far, an adequate electromotive force will be generated to cause the electroma net I6 to be energized sufficiently to move armature I08 down into engagement therewith. As soon as this takes place, switch blade I04 is separated from contact I05. It will be noted that the establishment of the circuits both to the solenoid winding 90 and the primary 20 of the transformer I9 are dependent upon the engagement of switch blade I 04 with contact I05. Accordingly, when the switch blade is thus separated from contact I05, both the solenoid winding 90 and the ignition transformer I9 are deenergized.

The deenergization of solenoid winding 90 permits the armature 88 to drop. Thus there is ,no longer a force applied to the left-hand end of lever 69. Due to the fact that the electromagnet I6 is now energized, the armature will beheld in engagement therewith inspite of the deen- Thus the biasing effect of spring I3 is overcome and the two biasing springs 61 and 56 are able to move their respective valves to open position, the lever60 now pivoting about the point I0.

The movement of valve 64 to open position permits the gas accumulated in the upper casing member 21 to pass out through passages 58 and 59, valve chamber 60, pipe 6|, valve 62, and pipe I5 to the bleed gas burner I4. Inasmuch as all of these passages are of much larger diameter than the passage 38 through the member 31, the gas is able to pass out of the upper casing faster than it is able to bleed into the same. The result is that the pressure on the under side of the diaphragm becomes greater than that on the upper side so that the valve 32 is moved oif of its seat. As soon as valve 32 is moved oil of its seat, the pressures on the two sides thereof are equalized with the result that an added lifting force results. Thus as soon as the valve leaves its seat, the valve is moved abruptly to full open poslton with a snap action. The opening of valve 32 admits gas to main burner I0, which gas is ignited by the pilot burner I2.

Under normal circumstances, the ignition means and the solenoid winding will not be brought into operation upon every call for heat. So long as the electromagnet I6 remains energized by reason of the pilot burner being ignited so that switch blade I04 is out of en agement with contact I05, the position of valve 32 will be controlled solely by the opening and closing of valve 02. The pilot burner I2 will continue to burn and it is only when the pilot burner is extinguished that the cycle which has just been described is performed.

It for any reason, it is desired to shut down the system, the switch I24 is opened which prevents energization of the winding 04 of the solenoid valve 62 and hence prevents opening of the main valve 32. In order, however, to extinguish the pilot, it is necessary to deenergize the electromagnet Ii. This is done by means of the switch comprising switch blade H3 and contacts III and II2. All that it is necessary to do is to push the push button II4 inwardly until switch blade II3 engages contacts III and H2. As previously stated, this results in the thermo-couple 02 being shorted out and almost immediately the electromagnet I6 becomes deenergized. This permits spring 13 to close the two valves 64 and 5|, thus extinguishing the pilot and absolutely precluding any chances of the main valve being opened even though solenoid valve 62 should be opened in some way or other.

It will be seen that I have provided a'new and novel burner control system in which the pilot burner is normally of the constant burning type but in which upon extinguishment of the pilot burner the same is automatically reignited upon a call for heat. It will further be seen that I have accomplished this in a relatively simple and inexpensive structure.

While I have shown a specific embodiment of my invention, it is to be understood that this is for purpose of illustration only and that the invention is to be limited only by the scope of the appended claims.

I claim as my invention:

1. In combination, a main valve, a pressure motor operatively connected to said valve, 8. con- .trol member controlling the pressure in said pressure motor and movable between a first position in which said main valve is closed and a second position in which said main valve is opened, electromagnetic means for controlling the position of said control member, said electromagnetic means comprising two members one an electromagnet and the other an armature and one of which is associated with said control member, said electromagnet being capable of holding but incapable of moving said members together, and supplementary power operated mo tor means for moving said electromagnet and said armature together.

2. 'in combination, a main valve, a pressure motor operatively connected to said valve, a control valve controlling the pressure in saidpressure motor and movable between a first position in which said main valve is closed and a second position in which said main valve is opened, electromagnetic means for controlling the position of said control valve, said electromagnetic means comprising two members one an electromagnet and the other an armature and one of which is associated with said control valve, said electromagnet being capable of holding but incapable of moving said members together, supplementary power operated motor means for moving said electromagnet and said armature together, and means for deenergizing said motor means upon energization of said electromagnet.

3. In a fluid fuel burner control system, a main burner, a pilot burner, a main valve controlling the flow of fuel to said main burner, a pressure motor operatively connected to said main valve, a control valve controlling the pressure in said pressure motor and movable between a first position in which said main valve is closed and a second position in which said main valve is opened, electromagnetic means for controlling the position of said control valve, said electromagnetic means comprising two members one an electromagnet and the other an armature and one of which is associated with said control valve, said electromagnet being capable of holding but incapable of moving said members together, a thermo-couple having its hot junction adjacent the pilot burner and connected to said electromagnet for energizing the electromagnet when the latter is ignited, and supplementary power operated motor means for moving said electromagnet and said armature together.

4. In a fluid fuel burner control system, a main burner, a pilot burner, a main valv controlling the flow of fuel to said main burner, a pressure motor operatively connected to said main valve, 9. control valve controlling the pressure in said pressure motor and movable between a first position in' which said main valve is closed and a second position in which said main valve is opened, electromagnetic means for controlling the position of said control valve, said electromagnetic means comprising two members one an electromagnet and the other an armature and one of which is associated with said control valve, said electromagnet being capable of holding but incapable of moving said members together, means responsive to a condition of the pilot flame controlling the energization of said electromagnet, supplementary power operated motor means' for moving said electromagnet and said armature together, and means operative upon said electromagnet becoming energized to deenergize said power operated means.

5. In a fluid fuel burner control system, a main burner, a, pilot burner, a main valve controlling the flow of fuel to said main burner, a pressure motor operatively connected to said main valve,

a control valve controlling the pressure in said said electromagnet being capable of holding but incapable of moving said members together, means responsive to a condition of the pilot flame controlling the energization of said electromagnet, supplementary power operated motor means for moving said electromagnet and said armature together, a thermostat responsive to the temperature of a controlling medium, and means including said thermostat operative when said thermostat is calling for heat and when said electromagnet is deenergized to energize said motor means.

6. In combination, a burner, a valve controlling the flow of fuel thereto, means biasing said valve towards closed position, means for overcoming the effect of the biasing means to hold said valve opened, said last named means comprising an electromagnet and an armature one of which is associated with said valve, means including a device responsive to a condition of said burner flame operative when said burner is ignited to energize said electromagnet sufficiently to hold but not to move said electromagnet and arma ture together, power operated motor means for moving said electromagnet and armature together, and means for deenergizing said motor means when said electromagnet becomes energized.

'2. In combination, a burner, a valve controlling the flow of fuel thereto, means biasing said valve towards closed position, means for overcoming the efiect of the biasing means to hold said valve opened, said last-named means comprising an electromagnet and an armature one of which is associated with said valve, means including a device responsive to a condition of said burner flame operative when said burner is ignited to energize said electromagnet sufficiently to hold but not to move said electromagnet and armature together, power operated motor means for moving said electromagnet and armature together, ignition means for said burner, and means operative upon a need for burner operation to energize said motor means and said ignition means if said electromagnet is deenergized.

8. In combination, a burner, a valve controlling the flow of fuel thereto, means biasing said valve towards closed position, means for overcoming the effect of the biasing means to hold said valve opened, said last-named means comprising an electromagnet and an armature one of which is associated with said valve, 2. thermo-couple having its hot junction adjacent to said burner and connected to said electromagnet so as to be operative when said burner is ignited to energize said electromagnet sufii'ciently to hold but not to .move said electromagnet and armature together, 7 power operated motor means for moving said electromagnet and armature together, and means for deenergizing said motor means when said electromagnet becomes energized.-

9. In combination, a main burner, a main valve controlling the flow of fluid'thereto, a normally constantly burning pilot burner, a pilot valve controlling the flow of fuel to said pilot burner and constituting the only means for interrupting the flow of fuel to the pilot burner, means including a device responsive to a controlling condition for controlling theoperation of said main valve to cause the same to move between closed and open positions, electromagnetic means the energization of which is controlled solely in accordance with a condition of the pilot flame for maintaining said pilot valve open whenever said electromagnetic means is energized as the result of the pilot burner being ignited, ignition means, and means for opening said pilot valve and energizing saiddgnition means whenever said condition responsive device is calling for opening of the main valve and said electromagnetic means is deenergized.

10. In combination, a main burner, a main valve controlling the flow of fluid thereto, a normally constantly burning pilot burner, a pilot valve controlling the flow of fuel to said pilot burner and constituting the only means for interrupting the flow of fuel to the pilot burner, means including a device responsive to a controlling condition for controlling the operation of said main valve to cause the same to move between closed and open positions, electromagnetic means the energization of which is controlled solely in accordance with a condition of the pilot flame for maintaining said pilot valve open whenever said electromagnetic means is energized as the'result of the pilot burner being ignited, means for causing both the closure of said pilot valve and said main valve when said electromagnetic means is deenergized, ignition means, and means for opening said pilot valve and energizing said ignition means whenever said condition responsive device is calling for opening of the main valve and said electromagnetic means is deenergized.

11. In combination, a main burner, a main valve controlling the flow of fuel thereto, means including a device responsive to a controlling condition for controlling the operation of said main valve, a pilot burner for igniting the fuel delivered to said main burner, a pilot valve controlling the flow of fuel to said pilot burner, electrically operated power means energized by said condition responsive device upon a demand for burner operation to open said pilot valve in the event that said pilot valve is closed at the time, means for igniting the fuel delivered to said pilot, said ignition means being energized by said condition responsive device substantially simultaneously with said electrically operated power means, and means responsive to heat from said pilot burner maintaining said pilot valve open independently oi said condition responsive device.

12. In combination, a main burner, a main valve controlling the flow of fuel thereto, means including a device responsive to a controlling condition for controlling the operation oi said main valve, a pilot burner for igniting the fuel delivered to said main burner, a pilot valve controlling the flow of fuel to said pilot burner, electrically operated power means energized by said condition responsive device upon a demand for burner operation to open said pilot valve in the event that said pilot valve is closed at the time, meansfor igniting the fuel delivered to said pilot, said ignition means being energized by said condition responsive device substantially simultaneously with said electrically operated power means, and pilot flame responsive means including means maintaining said pilot valve open independently of said condition responsive device so long as said pilot burner remains ignited and means preventing the opening of the main valve by said condition responsive device unless said pilot burner is ignited. I

DU WAYNE J. PE'IERSON. 

